Orthodontic aligners are commonly used to align teeth for aesthetic reasons. Each aligner must be customized to a patient individually as no two patients have identical teeth alignment. Clear aligners that appear nearly invisible when used are particularly popular among users who prefer discreet treatment and there is a significant demand for them globally. Clear aligners fit over a patient's teeth to apply forces that move the teeth from an original alignment to a desired alignment. In a treatment plan for an individual patient, depending on the amount of movement required, a number of aligners corresponding to different stages of alignment during the course of treatment may be used to move the teeth gradually from their original positions to the desired positions. This is because each aligner is limited in the amount of displacement that it can effect on the teeth.
Currently, to form a number of clear aligners for treatment of a single patient, an impression of the patient's teeth is first taken. The dental impression is scanned to obtain a digital model of the original alignment of the teeth. A treatment plan is then created, comprising a series of teeth digital models of the teeth at different stages of alignment between the original alignment and the desired alignment. A series of dental casts is then made, each corresponding to each of the teeth digital models in the treatment plan. The dental casts are typically made of a photopolymer using stereolithography followed by post-processing in which the dental casts may be washed with ethanol and post-cured with ultraviolet light. A series of aligners are then made from each of the dental casts. The aligners are typically made using thermoforming of a translucent biocompatible thermoplastic sheet onto the dental casts. Subsequently, the thermoformed thermoplastic sheets are removed from the dental casts and trimmed according to the teeth digital models using CNC machining and polished in order to form the aligners, before packaging, labelling and shipping to the patient.
Given the number of aligners required for each patent and the number of patients using such aligners internationally, it would be desirable to reduce the number of steps required to form each aligner to reduce manufacturing time and cost and also greatly reduce the logistical operations in the fabrication process.